A paramilitary is a semi-militarized force whose organizational structure, tactics, training, subculture, and (often) function are similar to those of a professional
military, but which is formally not part of a government's
armed forces.[1]

Though a paramilitary is not a military force, it is usually equivalent to a military's
light infantry force in terms of intensity, firepower, and organizational structure. A paramilitary may also commonly fall under the command of a military, even despite not being part of the military or play an assisting role for the military in times of war.

References

^"paramilitary". Oxford English Dictionary (3rd ed.).
Oxford University Press. June 2011 [online edition; original published in June 2005]. Retrieved 2011-09-13. Designating, of, or relating to a force or unit whose function and organization are analogous or ancillary to those of a professional military force, but which is not regarded as having professional or legitimate status.

Further reading

Golkar, Saeid. (2012). Organization of the Oppressed or Organization for Oppressing: Analysing the Role of the Basij Militia of Iran. Politics, Religion & Ideology, Dec., 37–41. doi:10.1080/21567689.2012.725661